M-APSK phase detection algorithm and parallel carrier synchronization method

In order to realize the precise phase correction of high order modulation in M-APSK modem, the Q-power non-data aided phase detection method recommended by DVB-S2 standard for 16APSK and 32APSK was extended to 64APSK, 128APSK and 256APSK. An improved algorithm was proposed to solve the problem of unstable loop operation when the proportion of constellation points used for phase detection in high-order modulation was low. By using threshold judgment on the amplitude of the received symbol after power normalization, phase detection was performed only when the amplitude was higher than the threshold, and the filter state and phase compensation value were not changed when the amplitude was lower than the threshold, so as to improve the phase detection effectiveness and reliability of constellation points and reduce the lock threshold. Aiming at the problem that the symbol rate of high-speed data transmission was very high but the working clock frequency of the processor was relatively low, a parallel carrier synchronization method for M-APSK was proposed, which could meet the needs of the receiver’s working clock. Compared with the traditional constant coding and modulation (CCM) carrier synchronization loop, the parallel method could also be applied to the frequency tracking of variable coding and modulation (VCM) system. © 2024 Editorial Board of Journal on Communications. All rights reserved.